Monolithic nonlinear transmission lines and sampling circuits with reduced shock-wave-to-surface-wave coupling

Abstract

A monolithic non-linear transmission line and sampling circuit with reduced shock-wave-to-surface-wave coupling are presented herein. In coplanar-waveguide (CPW) technology, this reduced coupling is achieved by selecting properly the thickness of the semiconductor substrate, and by elevating the center conductor of the CPW above the substrate surface. The elevated center conductor is supported by means of conducting posts, and may be backed by a low-loss dielectric such as polyimide or silicon nitride. In coplanar-strip (CPS) technology, the reduction in coupling between shock waves and surface waves is achieved by controlling the substrate thickness as in the CPW case, and by elevating the coplanar strips above the substrate surface. The elevated strips are supported by a low-loss dielectric. The reduced coupling in both guiding media enhances the high-frequency performance of nonlinear-transmission-line-based circuits. The semiconductor devices loading the CPW or CPS transmission lines may be Schottky diodes or some other type of variable-reactance device.

Description

FIELD OF THE INVENTION[0001]The current invention relates generally to the propagation of shock waves on non-linear transmission lines, and more particularly to monolithic nonlinear coplanar waveguides and strips with reduced coupling to surface waves.BACKGROUND OF THE INVENTION[0002]Monolithic non-linear transmission lines are used as shock-wave generators in numerous high-speed circuits, such as samplers of high-frequency signals. Early developments of shock wave propagation in non-linear transmission lines dealt with the effect of shock waves on parametric amplification. A representative of such developments is “Shock Waves in Non-Linear Transmission Lines and Their Effect on Parametric Amplification”, by R. Landauer, IBM Journal of Research, 1960. Since then, numerous applications of monolithic nonlinear transmission lines and derivatives of such have been developed. Generally, these applications related to the generation of pico-second pulses for the purpose of gating samplers ...

AI Technical Summary

Benefits of technology

[0007]A monolithic non-linear transmission line and sampling circuit with reduced shock-wave-to-surface-wave coupling are presented herein. In coplanar-waveguide (CPW) technology, this reduced coupling is achieved by selecting properly the thickness of the semiconductor substrate, and by elevating the center conductor of the CPW above the substrate surface. The elevated center conductor is supported by means of conducting posts, and may be backed by a low-loss dielectric such as polyimide or silicon nitride. In coplanar-strip (CPS) technology, the reduction in coupling between shock waves and surface waves is achieved by controlling the substrate thickness as in the CPW case, and by elevating the coplanar strips above the substrate surface. The elevated strips are supported by a low-loss dielectric. The reduced coupling in both guiding media enhances the high-frequency performance of nonlinear-transmission-line-based circuits. The semiconductor devices loading the CPW or CPS transmission lines may be Schottky diodes or some other type of variable-reactance device.

Problems solved by technology

Although nonlinear transmission lines having a top-contacted air-bridged center conductor have been developed, their ability to reduce shock-wave-to-surface-wave coupling has not been recognized.

In operation, these nonlinear transmission lines reduce high skin-effect losses at extremely short wavelengths, and result in shock waves having short fall times. The reduced shock-wave-to-surface-wave coupling resulting from the elevation of the center conductor above the substrate surface has not been recognized, nor has the effect of substrate thickness on this coupling mechanism.

Such coupling is highly undesirable as it can deprive a shock wave of its high-frequency harmonics, thus imposing a lower limit on the shock-wave falltime and amplitude.

In nonlinear-transmission-line-based samplers, such coupling increases unwanted leakage between the RF and strobe ports, and results in reduced sampler bandwidth and dynamic range.

These aspects, when left unchecked would limit the operation of nonlinear-transmission-line-based circuits.

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